1. Field of the Invention
The present invention relates to an HST unit including a pair of hydraulic motor units, each hydraulic motor unit being independently arrangeable, and a hydraulic pump unit forming a traveling hydrostatic transmission in cooperation with the pair of hydraulic motor units.
2. Related Art
It has been conventionally known to form a traveling hydrostatic transmission by fluidly connecting the hydraulic pump unit and the hydraulic motor unit, which are arranged spaced apart from each other, by way of a conduit.
Such configuration is particularly useful in a working vehicle needing to provide a space between a pair of driving wheels so as to stabilize the body posture at the time of turning such as a mower tractor capable of turning in place (zero turn) (for example, see U.S. Pat. No. 6,425,244).
However, with the conventional configuration, the hydraulic pump unit and the hydraulic motor unit have to be independently attached to the vehicle main body, and then be fluidly connected by the conduit, in the assembly work to the vehicle main body, resulting in a worse assembly workability.                Furthermore, the adjustment work of the traveling hydrostatic transmission configured by the hydraulic pump unit and the hydraulic motor units is desirably performed in a state where the hydraulic pump unit and the hydraulic motor unit fluidly connected according to the usage conditions. However, with the conventional configuration, such adjustment work can only be performed after the hydraulic pump unit and the hydraulic motor units are attached to the vehicle main body.        
Moreover, in some specified cases, a reservoir tank that is an oil source of the operational fluid in the traveling hydrostatic transmission may be provided. However, with the conventional configuration, the attachment of the reservoir tank to the vehicle main body also has to be performed independently from the hydraulic pump unit and the hydraulic motor units.
In view of the conventional techniques, the present invention aims to provide an HST unit that enhances the efficiency of the fluidly connecting work, the adjustment work and the attachment work to the vehicle main body, of the hydraulic pump unit and the hydraulic motor units configuring the traveling hydrostatic transmission.